High dopant activation in source/drain or tip regions of a semiconductor device can significantly improve device performance, i.e., by reducing Rext. Pulsed-laser anneal processes can produce highly active “superactive” regions in a device by melt and rapid regrowth of the doped region. These regions, however, are susceptible to deactivation by subsequent thermal processes.
While pulsed-laser “melt” anneal processes for source-drain formation are not common in high-volume manufacturing, available literature generally describes a pulsed-laser “melt” anneal process as including pre-amorphizing implant in source/drain (such as a silicon implant), a source-drain implant (such as a phosphorous implant), followed by the pulsed-laser anneal process. The pulsed-laser anneal process is targeted to melt the amorphous material without melting the underlying substrate in which the boundaries of the source and drain are defined by the amorphizing implant conditions. The melt process produces super-activated regions having abrupt, box-like dopant profiles. Another common, closely related technique omits the pre-amorphizing implanting step and relies on fine control of the laser energy to control the depth of the super-active region. Depending on species and precise process parameters, raw activation levels of up to 100% can be achieved.
One key challenge in integrating such processes is retaining high activation levels through the remainder of the manufacturing process. Deactivation from subsequent thermal processes reduces net activation back towards equilibrium levels in the final product, thereby reducing the overall benefit of the melt-and-anneal process.
It will be appreciated that for simplicity and/or clarity of illustration, elements depicted in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. The scaling of the figures does not represent precise dimensions and/or dimensional ratios of the various elements depicted herein. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.